NOTE: Many people find the construction "his or her" wordy, so if it is possible to use a plural noun as your antecedent and thus you can use "they" as your pronoun, it may be wise to do so. If you do use a singular noun and the context makes the gender clear, then it is permissible to use just "his" or "her" rather than "his or her."

2. Agree in person

If you are writing in the first person (I), don't confuse your reader by switching to the second person (you) or third person (he, she, they, it, etc.). Similarly, if you are using the second person, don't switch to first or third.

When a person comes to class, he or she should have his or her homework ready.

(INCORRECT: When a person comes to class, you should have your homework ready.)

3. Refer clearly to a specific noun.

Don't be vague or ambiguous.

INCORRECT: Although the motorcycle hit the tree, it was not damaged.

(Is "it" the motorcycle or the tree?)

INCORRECT: I don't think they should show violence on TV.

(Who are "they"?)

INCORRECT: Vacation is coming soon, which is nice.

(What is nice, the vacation or the fact that it is coming soon?)

INCORRECT: George worked in a national forest last summer. This may be his life's work.

(What word does "this" refer to?)

INCORRECT: If you put this sheet in your notebook, you can refer to it.